This invention relates to running shoe designs.
Historically, shoes have been designed for comfort and style with little concern for their effect on the biomechanics of the legs and feet. Recently, considerable emphasis has been placed on the development of improved shoes for running. Manufacturers of shoes have developed new combinations of materials and structures to improve cushioning, support, stability, flexibility, durability, and reduce weight.
Many shoe designs attempt to improve the support and stability given to a person's foot by conforming the shape of the inner sole to the shape of the bottom of the foot. For example, in U.S. Pat. No. 4,124,946 to Tomlin, the inner sole includes depressions for the heel and big toe and ridges under the arch of the foot and the area in front of the head of the metatarsals where the toes are joined with the remainder of the foot. A similar design for cradling the foot is shown in U.S. Pat. No. 4,133,118 to Khalsa, et al.
Other design features, instead of merely improving the support of the foot while standing, assist the rolling movement of the foot during running. For example, U.S. Pat. No. 4,348,821 to Daswick shows a rounded heel portion of the outer sole which enhances the original rolling motion of the heel after it strikes the ground. In addition, Daswick shows a second rounded portion of the outer sole which provides a second pivot point for the mid-portion of the foot to enable the mid-point of the foot to transform from a flat position to a take-off position by pivoting around this rounded portion. Other designs enchance the flexibility of the toe area to enable the bending of the foot in this area upon take-off.
Other designs of the outer soles of running shoes have been developed to increase traction while also improving resiliency and cushioning. Waffle and other patterns both improve traction due to the shape of the surfaces and increase cushioning by forming air pockets between the outer sole and the ground. A great deal of emphasis has gone into developing materials which have these properties. Shoe designs usually involve a compromise of features, such as a trade-off between cushioning and stability.